Proximity sensor devices (also commonly called touch pads or touch sensor devices) are widely used in a variety of electronic systems. A proximity sensor device typically includes a sensing region, often demarked by a surface, to determine the presence, location and/or motion of one or more fingers, styli, and/or other objects. The proximity sensor device, together with finger(s) and/or other object(s), can be used to provide an input to the electronic system. For example, proximity sensor devices are used as input devices for larger computing systems, such as those found integral within notebook computers or peripheral to desktop computers. Proximity sensor devices are also used in smaller systems, including: handheld systems such as personal digital assistants (PDAs), remote controls, communication systems such as wireless telephones and text messaging systems. Increasingly, proximity sensor devices are used in media systems, such as CD, DVD, MP3, video or other media recorders or players.
Many electronic devices include a user interface, or UI, and an input device for interacting with the UI (e.g., interface navigation). A typical UI includes a display for showing graphical and/or textual elements or other user feedback to input. The display may range from a vector driven CRT, or a scanned LCD, to individually controlled or backlit icons, and a variety of methods of providing visual user feedback. Other forms of feedback to input may also be used (e.g. audio and tactile) to provide modal information, selection acknowledgement, or action timing/ordering information. The increasing use of these types of UIs has led to a rising demand for proximity sensor devices as pointing devices. In these applications the proximity sensor device can function as a value adjustment device, cursor control device, selection device, scrolling device, graphics/character/handwriting input device, menu navigation device, gaming input device, button input device, keyboard and/or other input device.
Proximity sensor devices and capacitive sensors are commonly used as input devices for computers, personal digital assistants (PDAs), remote controls, media players, video game players, consumer electronics, cellular phones, payphones, point-of-sale terminals, automatic teller machines, kiosks and the like. Many proximity sensors use measurements of capacitance to detect object position or proximity (or motion or presence or any similar positional information). Capacitive sensing techniques are used in user input buttons, slide controls, scroll rings, scroll strips and other types of sensors. One other type of capacitance sensor used in such applications is the button-type sensor, which can be used to provide information about the existence or presence of an input. As discussed above, another type of capacitance sensor used in such applications is the touchpad-type sensor, which can be used to provide information about an input such as the position, motion, and/or similar information along one axis (1-D sensor), two axes (2-D sensor), or more axes. Both the button-type and touchpad-type sensors can also optionally be configured to provide additional information such as some indication of the force, duration, finger count, finger separation, or amount of capacitive coupling associated with the input. Imaging sensors with independent arrays of sensors may be used for multiple inputs for multi-finger position sensing, or for measuring relative motions. A variety of reporting, signaling, and methods of data reduction before transmission, as well as, polled or interrupt control methods may be used. A variety of fabrication and assembly methods may also be used including, flexible and rigid printed circuit boards, transparent conductors and substrates, as well as, methods of creating interconnects and vias. One example of a 2-D touchpad-type sensor that is based on capacitive sensing technologies is described in U.S. Pat. No. 5,880,411, which issued to Gillespie et al. on Mar. 9, 1999. Such sensors can be readily found, for example, in input devices of electronic systems including handheld and notebook-type computers.
A user generally operates a capacitive input device by placing or moving one or more fingers, styli, and/or objects, near a sensing region of one or more sensors located on or in the input device. This creates a capacitive effect upon a carrier signal applied to the sensing region that can be detected and correlated to positional information (such as the position(s) or proximity or motion or presences or similar information) of the stimulus/stimuli with respect to the sensing region. This positional information can in turn be used to select, move, scroll, or manipulate any combination of text, graphics, cursors and highlighters, and/or any other indicator on a display screen. Other visual, auditory, and tactile feedback methods can also be used for highlighting or display. The positional and/or temporal information can also be used to enable the user to interact with an interface, such as to control volume, to adjust brightness, or to achieve any other purpose.
Although capacitance sensors have been widely adopted for several years, sensor designers continue to look for ways to improve the sensors' functionality and effectiveness. In particular, engineers continually strive to improve the performance for the design and implementation of position sensors without increasing costs, pin count, electrode routing, component count, size, or complexity. Moreover, as such sensors become increasingly in demand in various types of electronic devices, a need for a highly-flexible yet low cost and easy to implement sensor design arises. In particular, a need exists for a sensor design scheme that is flexible enough for a variety of implementations and powerful enough to provide accurate capacitance sensing while remaining cost effective.
Accordingly, it is desirable to provide systems and methods for quickly, effectively and efficiently detecting a measurable capacitance. Moreover, it is desirable to create a design scheme that can be readily implemented using readily available components, such as standard ICs, microcontrollers, and discrete components. Other desirable features and characteristics will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.